Answer:
C. The bird population moved into and adapted to many different environments on the Hawaiian Islands.
Why:
When a species adapts itself to new environments certain features will change, such as beak size, wing use, and even height, these are all changed depending on what the species does and needs to survive. These birds all changed food sources which made them have to adapt their beaks over time to new sources, and natural color to over generations camouflage themselves better from predators.
(Hope this was a good explanation.)